Currently, packaging container disposal is at issue. Incineration disposal as in the case of general-purpose resins results in emission of carbon dioxide directly to the environment, and hence is not a good method. Methods of degradation by microorganisms present in the environment, such as landfill disposal, can be expected to reduce addition to the environment. However, such methods take time, and it is difficult to secure land therefor.
Meanwhile, there is proposed a method in which a molded article or the like made of a biodegradable resin is degraded by using an enzyme (see Patent Document 1). In addition, there is proposed a method for depolymerizing polylactic acid to produce oligomers mainly composed of repolymerizable cyclic compounds (see Patent Document 2).
Meanwhile, biodegradable resin compositions such as biodegradable polylactic acid-based resin compositions have been proposed as packaging materials. In general, a packaging container or the like using such a biodegradable resin composition is degraded sequentially from the surface of the container, and complete degradation of the entire container requires a considerable time. Moreover, since the degradation rate of a resin is affected by internal structures of the resin such as the crystallinity of the resin and the molecular orientation therein, there is a problem that the container has some part easy to degrade, but has other part difficult to degrade. In this respect, various biodegradable resin compositions have been developed recently in order to solve these problems. For example, there is reported a readily degradable resin composition with a biodegradability improved by blending an aliphatic polyester which releases an acid upon hydrolysis (Patent Document 3).
Patent Document 1: Published Japanese Translation of PCT International Application No. 2001-512504
Patent Document 2: International Patent Application Publication No. WO2004/013217
Patent Document 3: International Patent Application Publication No. WO2008-038648